IPCC Special Report on Emissions Scenarios

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4.5. Regional Scenario Patterns

The scenarios imply different regional patterns of socio-economic driving forces and resultant emissions. These are summarized in Table 4-19.

Following the definition of the four world regions adopted in this report, the industrial region (IND) corresponds to the SRES regions OECD90 and REF, and the developing region (DEV) corresponds to the SRES regions ASIA and ALM. In 1990, the base year of the SRES scenarios, driving-force variables as well as emissions are distributed unevenly. According to the statistics reported in Nakic�enovic� et al. (1998), DEV countries account for 76% of global population. However, they only account for 16% to 36% of global economic activity (considering GDP at market exchange rates and purchasing power parities, respectively), 34% of primary energy use, and 42% of global CO₂ emissions (including all sources, from energy plus land-use changes).

Over time, the regional distribution of socio-economic activities and emission shifts in the scenarios, albeit because of different driving forces. These shifts range from rapid population growth (scenario family A2) and rapid economic development and catch-up (scenario family A1) in developing countries, to rapid "dematerialization" of economic activities in industrial countries (scenario family B1). Generally, scenario family B2 depicts the most gradual changes, and hence also the slowest rates of change in the global distribution of activities and emissions. Of all the SRES scenarios, A2-A1-MiniCAM exhibits the slowest dynamics of development catch-up.

Table 4-19 summarizes the main scenario indicators differentiated between industrial and developing countries. Two measures are given (following La Rovere, 1998):

• Date when activities and/or emissions in developing countries reach those that prevailed in industrial countries in 1990.
• Date when developing country values equalize those of industrial countries.

In this comparison, developing countries in 1990 already accounted for 76% of world population and, because of the inevitable demographic momentum, their share is likely to increase further over the next few decades before alternative demographic projections branch out into different regional distributions. However, the basic pattern of dominance of developing countries in global population remains unchanged across all demographic projections. The share of developing countries in global population ranges between 80% (A1, B1) and 86% (A2, B2) by 2100 for demographic projections between 7 and 15 billion people. From the distribution of global population, the scenarios indicate an increasing importance of developing countries in the future, albeit at different rates.

In consequence, as shown in Table 4-19, total GDP expressed at purchasing power parities in developing countries could reach 1990 levels in industrial regions between 2000 and 2010 and equalize future industrial country levels between 2010 and 2030. For GDP expressed at market exchange rates, the 1990 "parity date" is reached between 2015 and 2030 and equalization in absolute terms even later, between 2030 and 2060. Total primary energy use in developing countries could reach 1990 industrial levels between 2005 and 2010, and parity in absolute terms between 2005 and 2020. Possible spatial distributions of economic activities based on satellite night imagery data that correlate highly with, for example, GDP and electricity use are discussed in Box 4-10.

Conversely, scenario per capita indicators converge only slowly, sometimes well after 2100. Per capita GDP (expressed at market exchange rates) of developing countries reaches the 1990 level of industrial countries at the earliest around 2050 (scenario family A1) and well after 2100 in scenario family A2. None of the four marker scenarios projects a situation in which per capita income in developing countries surpasses future levels of per capita incomes of Annex I countries. Energy use per capita shows a similar pattern. Only scenario family A1 depicts a development in which per capita energy use in developing countries could approach that prevailing in industrial countries in 1990 (by 2070) and in which it could reach parity with industrial countries in the very long-term (after 2100). In all other scenarios energy use per capita remains below 1990 or future per capita energy use levels of industrial countries. By and large, these scenario features reflect the very large differences in present per capita levels of economic activity and energy use, which require many decades, even a century, to narrow. The scenarios thus portray a feature known as "slow conditional convergence only" in the development literature (see, e.g., Shin, 1996).

Concerning GHG emissions, discussed in more detail in Chapter 5, trends reflect the evolution of scenario-driving forces discussed above. CO₂ emissions of developing countries reach levels in industrial countries around or shortly after the year 2000. This reflects the continued growth in energy use (and emissions), slow recovery of economies in transition (and thus modest growth in aggregate emission from industrial countries), and a continuation of current trends in land-use changes (deforestation); these only diverge in the medium- to long-term across the SRES scenarios.

Yet, even with equalizing total emission levels, regional differences in cumulative and per capita emissions remain pronounced. Based on the estimates of cumulative CO₂ (all sources) emissions since 1800 given in Gr�bler and Nakic�enovic� (1994), developing countries reach 1990 levels of industrial countries only between 2015 and 2030. They reach parity (historical data from 1800 to 1990, and scenario values from 1990 onward) at earliest by 2040 (scenario family A1), and between 2050 (A2 and B1) and post-2100 (scenario family B2) in the other scenarios. None of the SRES scenarios reaches the 1990 per capita CO₂ emissions levels of industrial countries in the developing countries.

In scenarios with vigorous climate policies (not in the SRES terms of reference) per capita emissions levels in industrial countries may approach levels as projected for developing countries. However, no scenario without climate policies could be found in the literature in which per capita emissions in industrialized and developing countries reached similar levels. Thus the absence of such convergence in the SRES scenarios reflects the current literature, and results from the nature of the SRES scenarios as "no climate policy" scenarios.

SRES scenarios do follow the recommendation to explore possible pathways of closing the income gap between the industrial and now developing regions (Alcamo et al., 1995). For reasons of plausibility and foundation in the reviewed no-climate- policy literature, the SRES scenarios do not achieve full income convergence in the scenario period analyzed. However, income levels in developing countries do reach the 1990 levels of the industrial countries in the second half of the next century in three out of four scenario families.